Pulpstone



May 15, 1956 W. F. BETH 2,745,226

PULPSTONE Filed May 31, 1955 2 Sheets-Sheet l INVENTQR. HALTER f.' Bfr/f n 3;', Arran/v W. F. BETH May 15, 1956 PULPSTONE 2 Sheets-Sheet 2 Filed May 3l, 1955 v Ton.

ETH

/l 7' Toe/var United safes Parent-o PULPsroNE Walter F. Beth, Worcester, lMass., assigner to Norton Company, Worcester, Mass., a corporation of Massachusetts t Application May 31, 1955, Serial No. 511,832

6 Claims. (Cl. 51-206.5)

The invention relates to pulpstones.

the blocks of which are not under strain but which are nevertheless held to the center with little possibility of play developing. Another object of the invention is to provide a pulpstone especially adapted for use inY grinders of more than usual horsepower. Another object is to provide a pulpstone of rugged characteristics ablefto` withstand heavy duty. Another object is to provider a superior pulpstone having a steel center whichcan be used for reconstruction after the pulpstone has worn out. Another object is to provide a pulpstone construction permitting the ready replacement of broken blocks.

Other objects will be in part obvious -or in part pointed out hereinafter.

In the accompanying drawings illustrating the invention, Figure 1 is a fragmentary view, partly in end elevation and partly in section, of a pulpstone constructed in accordance with the invention,

. FigureZ is a view similar to Figure 1 illustrating a slightmodiication of Figure 1,

Figure 3 is a sectional view illustrating one mannerof setting the bolts in the blocks,

VFigure 4 is a bottom View of one type of block usedvfactured, sold and used, and patents illustrating and describing them were issued, in which the blocks, also called segments, were secured to a steel drum by bolts of various kinds. As the performance demanded of these pulpstones 2,745,226 I `Patented May 15, 1956 designated by the reference character 10.y Each bolt has .threaded heads 12 of thetype disclosed in the Howe and preferably somewhat larger than the metal threads 14. The'formation ofthe threaded holes in the pulpstone ,y g 15 One object of the invention is to provide a pulpstone.

v being common.` y

and 8, the blocks 19 inwardly of the stone are regular cylindrical.

increased, by the use of driving motors in the pulp grinders i of greater horsepower, breakage of the blocks became serious. To meet this situation the concrete center pulp-v stones were developed and, in many different forms, were manufactured, sold, used and patented. An excellent example of a concrete center pulpstone is illustrated'and described in U. S. Patent No. 2,421,885 to Howe and Washburn.

have discovered that a superior pulpstone for use in grinders of more than average horsepower can be produced bythe utilization ofa steel or iron drum center,

bolts under initial tension andblocks not under initialv tension. j

Referring now to Figures l to 5 inclusive, the bolts are v`rblocks 19 and 20 is described in the Howe and Washburn patent and'hence'need notbe repeated herein. The blocks 19 and 20 are made of vitried bonded abrasive material "the nature of which is nowxfully understood in the art.

For rpulpstone blocksboth fused aluminum oxide and silicon carbide .have been used and eachvis used today. The desired abrasive is mixed with ceramic bonding material usually. involving a majorfportion of clay, the blocks are molded from the mixture of abrasive and ceramic material and tare thentvitried in a kiln. Such manufacture being' well known it need not be` further herein described. Y 7

Inthe embodiments of the invention illustrated in the drawings the pulpstone blocks 19 and 20 are secured to a steel Vdrum 21 by lmeans of the bolts 10 as shown. Broadly speaking the drum 21 is a metal drum and any suitable steel or cast iron could be used or other metals such as bronze could be used. However, for manufacturing reasons Il prefer to use a cast iron of the kind known as semi-steel. Strength is, of course, important and yso isvrnanufacturing cost.

The drum 21 is a hollow metal cylinder. Any suitable mounting apparatus can be used, many being known in the art, and if desired the drum 21 can have spokes, or flanges can be used removably to secure it to the shaft of the pulp grinder. The blocks 19 and 20 can be of any desired contourin development, rectangles, squares and hexagons However, as shown in Figures 4, 5, 6

hexagonal blocks 19 while the marginal blocks 20 are ve sided as shown'` By this construction the ends of the pulpstone can be plane surfaces or other surfaces of revolution.

The outer surfaces of the blocks will be at least eventually cylindrical and preferablythe inner surfaces will also be As shown in Figure 5 the bolts 10 are located in the exact centers of the blocks 19. As shown in Figure 4 the bolts 10 are located inthe approximate centers of the blocks 20 being on a center line between the two parallel sides and close to the center of gravity. They i are centrally locatedin the blocks 20 as well as inthe blocks 19.

Referring now to Figure 3, I insure the normal alignment of the bolts 10 by assembling each bolt with an inner washer l25, a pipe 26, and a nut 27 on the outer threaded endr28y of the bolt 10. The nut 27 is tightened and thruststhe washer 25 against the threaded head 12 (which has a shoulder) and as the bolt 10 including the head 12 wascarefully machined, the washer 25 will have a surface perpendicularto the axis of the bolt 10.

Prior to screwing the heads y12 of the bolts 10 onto the holes 17, I set the blocks 19 and 20y with the holes 17 up and ll the holes A17 with liquid resin which is poured olf l after a short time to allow it to penetrate into the abrasive somewhat. Then the heads 12 are screwed into the holes 17 Vby using the nuts 27. The heads 12 are screwed into i devices properly to aligneach bolt y10. At this time the holes 17 untilthe washers 25 contact the blocks 19 and 20 which happens before the heads 12 contact the ends of the holes 17 andthus the washers act as aligning Illustratively they avoidV excessive tightening of the bolts 10 in order to avoid placing the abrasive under strain. Then the blocks 19 and 20 are placed in an oven and cured to set the resin. Any suitable resin can be used but I have found that liquid stage phenol-formaldehyde resin mixed with a filler, for example 50% of silica fines, gives very good' results. Curing of this resin is-well known and illustratively can be at a top oven temperature of about 150 C. During the curing of the liquid resin to form solid resin, any strains between the threaded heads 12 and the abrasive are relieved so that when the blocks come out of the oven the bolts 10 are set therein without any substantial pre-tension.

The drum 21 has holes 31 extending therethrough in radial directions and spaced the Vproper-distance apart to receive the bolts 10 of all the blocks 19 and 21)'` required to build the pulpstone.v For constructing the pulpstone of Figure l which is further illustrated in Figures 6, 7 and 8, I provide elastic stop nuts 32 and utilize the washers 25 which tit in at recesses 33 formed in each of the blocks 19 and 2). I further provide a room temperature cement and I have found that an epoxy resin which is bisphenol epichlorhydrin resin for example sold under the trademark Araldite is satisfactory and the best one known to me. Before setting any block in place the nuts 27 are removed and so are the sleeves 26. Before painting an area of the drum 21 with the cement, I mask otf areas around the holes 31 equal to the size of the washers 25 and this may bedone with any masking paper or cloth cut into discs and many suitable materials are known. I paint only a limited part of the drum since the cement mentioned sets in twenty or thirty minutes and I want to set the blocks in place before the cement has set.

Having painted a limited area of the drum, and having removed the nuts 27 and the pipes 26 from the bolts 10 of a sufficient number of blocks 19 and 20 to coverv the area painted, 1 remove the masking discs not shown and put the blocks 19 and 2li in place with the bolts 1) through the holes 31, then place the elastic stop nuts on the bolts 10 inside of the drum 20 and tighten them with a torque of about 100 foot pounds which is found to be a good torque and sets a pre-tension in the bolts 10 with a suitable pitch of the threads 28 of around 6,000 pounds actual tensile stress which, however, is on the bolts 10 as the heads 12 and the washers 25 keep the tensile stress from the blocks 19 and `20. rhis procedure is repeated over and over again until the entire stone vhas been builtk by masking a number of areas around the holesl 31, painting a limited area with cement, placing blocks 19 or 20 in position with the bolts 10 through the holes 31, then applying and tightening the nuts 32. Instead of stop nuts 32 I might use a nut with lock washers or a pair of nuts as desired. The tensile stress in the bolts 10 and absolute units should be at least 3,000 pounds and not more than the bolts can stand.

Contrary to the usual practice I contemplate no tiller between blocks on any sides thereof. Perfect fitting being impractical, there is a clearance 35 between adjacent blocks and I nd one sixteenth of an inch to be a practical clearance. Of course in some cases the blocks might touch leaving a greater clearance on opposite sides of each but I prefer to employA small strips of Wood as spacers duringv assemblyr to `keep the clearances approximately equal. In use the clearance spaces will be partially filled with pulp.

I prefer to have only one bolt 14D for each block 19 and 2t) but within the scope ofthe invention in one asA pect more canl be used'. With only' one bolt per block the blocks can be quite small relative to the sizes of the drum 21. Replacement of broken blocks then becomes an easy matter especially when no filler between blocks is provided.

One advantage of the pulpstone. construction of this invention is that, when the abrasive of the blocks 19 and 20 has been used right down to the tops of the threaded heads 12 of the bolts 10, the pulpstone can be reconstructed in the paper mill without shipping the drum 21 back to the manufacturer. The nuts 32 are removed, then the worn out blocks 19 and 20 can be removed using hammers to loosen them, whereupon the cement on the outer surface of the drum 21 can be cut olf and then a new stone can be built by the procedure already described.

Figures 7 and 8 show an illustrative manner of mounting the pulpstone of the invention. Shafts 40 and 41 having tianges 42 are bolted by bolts 44 to a center 21 at the end thereof. Preferably the anges 42 have inwardly projecting cylindrical portions 46 nicely fitting the insides of the drum 21 to support it accurately. The shafts 40 and 41 are mounted in bearings in the pulpstone grinder. One of these shafts such as the shaft 41 is a driving shaft and has a driving flange 48' secured thereto as by means of a key and the flange 48 is coupled to the motor of the pulp grinder. These features are given only by way of illustration and may be varied at will.

In the modification of Figure 2, the washers 25 are not utilized after the bolts 1l) are set in the blocks 19 and 20 although they are utilized to align these parts as already described. The shoulders of the slightly longer heads 12a Contact the drum 21 and allow the nuts 32 to put the bolts 10 under the required tensile stress without stressing the threads 14 against the abrasive threads 16. In this case since the area of contact between the heads 12 and the drum 21 is so small the masking can be dispensed with. Figures 4 to 8 inclusive as well illustrate the pulpstone vconstructed according to the slight modication of Figure 2 as they do the pulpstone according to Figure 1.

In all embodiments of the invention the heads 12 and 12a or equivalent are unstressed relative to the pulpstone blocks when the pulpstone is completed and thereafter when it is not running. This is because the cement 34' can iiow during the tightening of the nuts 32 and therefore no matter how tight the nuts 32 may be, there is no tension developed of any appreciable significance betweenv the heads 12 or 12a and the blocks 19 and 20 since each block is placed in position before the cement 34 has set and the shoulders of the heads 12 and 12a with or Without the washers 25 prevent the blocks from being drawn inwardly far enough to make actual contact with the iron.

With regard to the cement between the blocks and the drum, I may use other room temperature setting organic cements and I can also use room temperature setting mineral cements of any kind. However, inorganic cements ,might also be used. Portland base cements, especially with an iron filler, are satisfactory. With regard to the resin in the threaded holes in the pulpstone blocks any `other organic resin could be used and there are many..

Room temperature mineral cements might also be used there.

While as stated pulpstone blocksof other shapes can be used Within the broad features of my invention, there is an advantage in using hexagonal blocks with five` sided marginal intertting blocks. This enables me to use small blocks nicely balanced with the bolts centrally located to avoid excessive strains in use and shapes approaching regular hexagons or being such in development or in chordal section are preferred as thereby no developed dimension of a block need be very much greater than any other dimension thereof. As illustrated the blocks 19 are regular hexagons in development (see Figure 8) although for manufacturing reasons it will probably be preferred to have them regular hexagons in sections cut by chordal planes that extend through edges of the blocks which are elements of the outer cylindrical surfaces thereof. In the claims the inner` blocks 19 are stated to be hexagons or that they are hexagonal which means that they are such in plan and in development,l In stating that the intertting blocks are ve sided blocks,

the linear sides are referred to as the blocks are seen in development.

The inner abrasive unit for the pulpstone of tion with its holding bolt in the preferred form of the invention may be described as consisting of a regular hexagon block of vitrified bonded abrasive material having a convex cylindrical surface having six plane surfaces extending from said convex cylindrical surface forming three dihedral angles whose apexes are on the concave side of said convex cylindrical surface, said block having one more surface truncating said dihedral angles, and a holding bolt extending into said block through the one more surface, said holding bolt having an enlarged threaded head the thread of which has a pitch of at least .080, said block having a threaded hole to receive said threaded head with which it is in screw threaded engagement, said bolt being in all of the'planes that bisect the dihedral angles, said threaded head being cemented into said threaded hole.

The outer abrasive unit for the pulpstone of the invention with its holding bolt in the preferred form of the invention may be described as consisting of a block of vitried bonded abrasive material having a convex cylindrical surface with five sides four of which are sides of a hexagon and the fifth of which is a straight side, said block having starting from the two sides adjacent the straight side two plane surfaces extending from'said convex cylindrical surface forming a dihedral angle whose apex is on the concave side of said convex cylindrical surface, said block having two other sides starting from the cylindrical surface and vtapering inwardly, said block having a plane side starting from the straight side of the convex cylindrical surface, said block having one more surface truncating the dihedral angle, and a holding bolt extending into said block through the one more surface, said holding bolt having an enlarged threaded end of the thread of which has a pitch of at least .080", said block having a threaded hole to receive said threaded head with which it is in screw threaded engagement, said bolt being in the plane that bisects the said dihedral angle and located well inwardly of the sides that extend from the cylindrical surface and being centrally located in said block, said threaded head being cemented into said threaded hole.

The blocks 19 and the blocks 20 have, inthe preferred form of the invention, the geometrical yfeatures described herein and illustrated in the drawings and it is preferred that the surface adjacent the drum 21 be cylindrical pre- .ferably with the centrally located recess 33 which has a flat bottom.

It will thus be seen that there has been provided by this invention a pulpstone in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the'above invention and as many changes might be made in the embodiments above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

l. A pulpstone comprising a metal drum having radial holes therethrough at regularly spaced intervals, a set of abrasive pulpstone blocks with threaded holes of shape, size and number to cover the major portion of the outer the invenholes and in threaded engagement with said blocks, there being at least one bolt for each block and. each bolt extending through one of the holes in the drum, and nuts on the bolts inside of said drum said nuts being tightened to place said bolts under absolute stress of at least 3,000 pounds, said threaded heads being held by said drum to stop the tensile stress from'extending into the heads and there being substantially no tension between the heads and the blocks with the pulpstone at rest, and room temperature setting cement between the outside surface of the drum and the adjacent surfaces of the blocks.

2. A pulpstone as claimed in claim l infwhich the heads are cemented in the threaded holes in the blocks l blocks.

4. A pulpstone as claimed in claim l in which the inner blocks are hexagons with interfitting marginal five sided blocks, and the bolts are centrally located in the blocks.

5. A pulpstone block and holding bolt therefor consisting of a hexagonal block of vitrified bonded abrasive material having a convex outer cylindrical surface, said block having six plane surfaces extending from said convex cylindrical surface forming three dihedral angles whose apexes are on the concave side of said convex cylindrical surface, said block having one more surface truncating said dihedral angles, and a holding bolt extending into said block lthrough the one more surface, said holding bolt having an enlarged threaded head the thread of whichhas a pitch of at least .080, said block having a threaded hole to receive said threaded head with which it is in screw threaded engagement, said bolt being in all of the planes that bisect the dihedral angles, said threaded head being cemented into said threaded hole.

6. A pulpstone block and holding bolt therefor consisting of a block of vitrified bonded abrasive material having aconvex cylindrical surface with ve sides four of which are sides of a hexagon and the fifth of which is a straight side, said block having starting from the two sides adjacent the straight side two plane surfaces extending from said convex cylindrical surface forming a dihedral angle whose apex is on the concave side of said convex cylindrical surface, said block having two other sides starting from the cylindrical surface and tapering inwardly, said block having a plane side starting from the straight side of the convex cylindrical surface, said block having one more surface truncating the dihedral angle, and a holding bolt extending into said block through the one more surface, said holding bolt having an enlarged threaded end the thread of which has a pitch of at least .080", said block having a threaded hole to receive said threaded -head with which it is in screw threaded engagement, said bolt being in the plane that bisects the said dihedral angle vand located well inwardly of the sides that extend from the cylindrical surface and being centrally located in said block, said threaded head being cemented into said threaded hole.

No references cited. 

1. A PULPSTONE COMPRISING A METAL DRUM HAVING RADIAL HOLES THERETHROUGH AT REGULARLY SPACED INTERVALS, A SET OF ABRASIVE PULPSTONE BLOCKS WITH THREADED HOLES OF SHAPE, SIZE AND NUMBER TO COVER THE MAJOR PORTION OF THE OUTER SURFACE OF SAID DRUM LEAVING HOWEVER NARROW SPACES BETWEEN ADJACENT BLOCKS, HOLDING BOLTS WITH THREADED HEADS WITH PITCH OF AT LEAST .080" SCREWED INTO SAID THREADED HOLES AND IN THREADED ENGAGEMENT WITH SAID BLOCKS, THERE BEING AT LEAST ONE BOLT FOR EACH BLOCK AND EACH BOLT EXTENDING THROUGH ONE OF THE HOLES IN THE DRUM, AND NUTS ON THE BOLTS INSIDE OF SAID DRUM SAID NUTS BEING TIGHTENED TO PLACE SAID BOLTS UNDER ABSOLUTE STRESS OF AT LEAST 3,000 POUNDS, SAID THREADED HEADS BEING HELD BY SAID DRUM TO STOP THE TENSILE STRESS FROM EXTENDING INTO THE HEADS AND THERE BEING SUBSTANTIALLY NO TENSION BETWEEN THE HEADS AND THE BLOCKS WITH THE PULPSTONE AT REST, AND ROOM TEMPERATURE SETTING CEMENT BETWEEN THE OUTSIDE SURFACE OF THE DRUM AND THE ADJACENT SURFACES OF THE BLOCKS. 